1. Technical Field
Example embodiments relate generally to semiconductor integrated circuits, and more particularly to a method and circuit for self-training of a reference voltage, and a memory system including the circuit.
2. Discussion of the Related Art
In comparison with a semiconductor device receiving a differential signal, a semiconductor device receiving a single-ended signal typically requires a reference voltage for determining a logic level of a received signal. It is desirable to set the voltage level of the reference voltage to a mean value of the low voltage level and the high voltage level of the received signal.
A semiconductor device adopting single-ended signaling or pseudo-differential signaling may compare the voltage level of the received signal with the reference voltage using a reception buffer including a comparator. The reception buffer may generate an internal signal of the logic high level when the voltage level of the received signal is higher than the reference voltage and generate the internal signal of the logic low level when the voltage level of the received signal is lower than the reference voltage. The generated or buffered internal signal is transferred to an internal circuit of the semiconductor device.
If the voltage level of the reference voltage is improper or inaccurate, errors may increase in determining the logic levels of the received signals and thus performance of the system may be degraded. The setup and hold times for latching the received signal are shortened as the data transfer rate is increased and thus the reference voltage of a more accurate level is desirable.